As a protection device for reducing the impact to occupants in the event of a frontal collision of an automobile, an airbag apparatus has been widely known. A conventional airbag apparatus is attached in a steering device or an instrument panel provided in front of the occupant, and in the event of a frontal collision of an automobile, the airbag is inflated at the front side of a driver seat and a front passenger seat to thereby restrain occupants sitting in the driver seat and the front passenger seat from moving to the front side. As a result, the occupants in the driver seat and the front passenger seat are effectively protected at the frontal collision of the automobile.
In recent years, protecting an occupant in an automobile at a side impact of the automobile also has been considered important. Thus, so-called side airbag apparatuses and curtain shield airbag apparatuses have been mounted in vehicles. Specifically, as shown in FIG. 10 for example, at the front passenger seat-side of an automobile 1, a curtain shield airbag apparatus 2 is placed so as to inflate at the neighborhood of the inner side of the glass at the upper portion of a front door 1a. A side airbag apparatus 3 is placed so as to inflate at the neighborhood of the inner side of the lower portion of the front door 1a. In FIG. 10, although the curtain shield airbag apparatus 2 and the side airbag apparatus 3 are shown only at the front passenger seat-side, the curtain shield airbag apparatus 2 and the side airbag apparatus 3 are also provided at the driver seat-side in an actual case.
When another vehicle 4 laterally collides with the automobile 1 as shown by the arrow X in FIG. 10, the curtain shield airbag apparatus 2 and the side airbag apparatus 3 are respectively inflated at a position close to the inner sides of the front door 1a, i.e., an outer region of the front passenger seat, to thereby protect the body of the occupant of the front passenger seat from having a direct contact with the front door 1a. 
On the other hand, Patent Publication 1 discloses an airbag apparatus that is attached in the ceiling of the vehicle interior and that is designed, in the event of a frontal collision of an automobile, to inflate downwardly to the front side of the occupant.
Patent Publication 2 discloses an airbag apparatus that is provided in a console between a driver's seat and a front passenger seat and that is designed to inflate, in the event of side collision of the automobile for example, between the seat back of the driver's seat and the seat back of the front passenger seat.
Patent Publication 3 discloses, for example, an airbag apparatus that is attached in an instrument panel in front of the front passenger seat and that is designed so that the airbag body is inflated at the front side of the occupant of the front passenger seat in the event of side collision of the automobile, a panel member provided in the vicinity of the ceiling is rotated in the lower direction, and a part of the airbag body inflated to the inner side of the vehicle interior is restricted from being moved to the rear side in the vicinity of the ceiling so as to be prevented from being inflated between the head of the occupant and the ceiling.
Patent Publication 4 discloses, for example, an airbag apparatus that is attached in the instrument panel in front of the front passenger seat, that is designed so that the main airbag body divided to left and right portions is caused, at the frontal collision of the automobile, to inflate in front of the occupant of the front passenger seat and the ceiling airbag body provided in the vicinity of the ceiling of the front passenger seat is caused to inflate in the lower direction and is engaged with a space between the divided left and right portions of the main airbag body inflated to the inner side of the vehicle interior to restrict the dislocation of the main airbag in the lateral direction to thereby prevent the main airbag from inflating in an unexpected direction.
However, in the event of side collision as shown in FIG. 10, an occupant at the opposite side of the side collision, i.e., the occupant in a driver's seat in the figure, may suddenly move to collision side as shown by the arrow A due to the backlash of the side collision.
On the other hand, the airbag apparatus according to Patent Publication 1 is configured so that the airbag is inflated from the ceiling to the front side of the occupant in a rear seat so as to protect the occupant from the frontal collision. However, this airbag apparatus is not configured so as to restrict the occupant at the side collision from moving to the collision side.
Furthermore, the airbag apparatuses according to Patent Publication 2 and Patent Publication 3 also have an objective of protecting an occupant at a frontal collision and are not configured so as to suppress, at a side collision, the occupant from moving to the collision side.
Thus, a center airbag apparatus has been suggested in recent years that causes an airbag to inflate between two seats.
In the airbag apparatus according to Patent Publication 4, the inflation at a side collision for example between the seat back of the driver's seat and the seat back of the front passenger seat prevents the situation where the occupant is caused by the impact load to fall to a side at which the impact is not sensed and has a contact with the neighboring occupant for example.
Patent Publications 5 and 6 also disclose a center airbag apparatus by which an airbag is caused to inflate at a side collision between the seat back of the driver's seat and the seat back of the front passenger seat.    Patent Publication 1: JP2000-185618A    Patent Publication 2: JP2005-067272A    Patent Publication 3: JP2005-145225A    Patent Publication 4: JP2004-217109A    Patent Publication 5: JP2008-114713    Patent Publication 6: JPH7-267037